1. Field of the Invention
The present invention relates to an input device which makes use of a change in electrostatic capacitance and which is suitable for use in, for example, a personal computer or a remote controller.
2. Description of the Related Art
Various types of input devices relying upon changes in electrostatic capacitance have been proposed in a variety of industrial fields including automotive industries, electric machinery industries, machine industries, civil engineering industries, and so forth. This kind of input devices permits input operations through appropriate changes of electrostatic capacitance, regardless of any change in the ambient temperature.
In operation of such a proposed input device, an operator""s finger touches a key top to slide it in a horizontal direction, so that an elastic member connected to the key top is deformed to change the size of a gap formed between a movable electrode formed on the elastic member and a fixed electrode opposing the movable electrode.
This change in the gap size causes a change in the electrostatic capacitance formed between the movable electrode and the fixed electrode, which in turn causes, for example, a movement of a cursor on a personal computer display.
There is an increasing demand for a downsizing of this kind of input device, particularly when the device is contemplated to be used for small-sized devices such as a personal computer or a remote controller.
Downsizing of the input device naturally limits the horizontal stroke of the key top. The user is therefore obliged to delicately operate the input device so as to implement, for example, a desired movement of a cursor on a personal computer display with a very small displacement of the key top. Thus, the operability is impaired and a long time is required to move the cursor exactly to desired position.
Downsizing of the input device naturally reduces the areas of the movable electrode and the fixed electrode, leading to a correspondingly smaller amount of change in the electrostatic capacitance caused by the key top operation. This makes it difficult to sense the change in the electrostatic capacitance, resulting in an inferior sensing precision.
Accordingly, it is an object of the present invention to provide an input device which, despite a reduced size, provides a horizontal stroke for a key top large enough to ensure superior operability, thereby overcoming the above-described problem.
It is also an object of the present invention to provide an input device which has a reduced size but is yet capable of providing an ample amount of change in the electrostatic capacitance, thus offering a high degree of accuracy of inputting operation, thereby overcoming the above-described problem of the known art.
To these ends, in accordance with one aspect of the present invention, there is provided an input device, comprising: a fixed electrode having a plurality of fixed electrode segments that are sensitive to a vertical inputting operation and a horizontal input operation; an elastic member which is provided, at least at a portion thereof facing the fixed electrode across a predetermined gap, with a conductive movable electrode, the elastic member being deformable so as to vary the size of the gap in response to an input operation; and an input operating section on which the input operation is to be performed, the input operating section being connectable to a coupling portion of the elastic member, whereby, when the input operating section is moved in a horizontal direction, the size of the gap formed between the electrode segments sensitive to the horizontal input operation is varied.
This arrangement permits a horizontal movement of the input operating section to be detected with a high degree of accuracy, thus offering a high inputting precision of the input device.
Preferably, the coupling portion of the elastic member has an elastically deformable flange extending outward from the outer peripheral end thereof, and the input operating section is coupled with the coupling portion having the flange. The flange is elastically deformed in response to a horizontal movement of the input operating section, thus affording a large stroke of horizontal movement of the input operating section. This offers a pleasant feel of manipulation of the input operating section when the same is moved in a horizontal direction.
The input device may further comprise a horizontally movable slider provided on the elastic member. In such a case, the input operating section is operatively connected to the elastic member through the slider, with the flange of the coupling portion being in fitting engagement with a fit hole formed in the slider so as to be vertically movable. A horizontal movement of the input operating section causes the inner peripheral wall of the fit hole to press the flange of the elastic member, whereby the flange and the movable electrode on the elastic member are elastically deformed to cause the variation in the size of the gap. With this arrangement, the movement of the input operating section is transmitted to the elastic member through the slider with a high degree of accuracy. It is therefore possible to achieve a further improvement in the inputting precision of the input device.
The input operating section may be arranged so as to be rotatable about the axis of the coupling portion of the elastic member. When a user attempts to move the input operating section in a horizontal direction with his finger placed on the outer periphery of the input operating section, a rotational force is applied to the input operating section. The rotational nature of the input operating section conveniently accommodates this rotational force to offer a pleasant feel of operation.
The input operating section may be provided with a vertical input portion formed at a portion thereof facing the fixed electrode segment sensitive to vertical input operation, whereby pressing of the portion of the input operating section causes a variation in the gap between the movable electrode and the segment of the fixed electrode sensitive to the vertical input operation.
This arrangement permits a vertical movement of the input operating section to be detected with a high degree of accuracy, thus offering a high inputting precision of the input device.
In accordance with another aspect of the present invention, there is provided an input device comprising: a fixed electrode having a plurality of electrode segments which are spaced in the circumferential direction and which are sensitive to input operations in horizontal directions; an elastic member which is provided, at least at a portion thereof facing the fixed electrode across a predetermined gap, with a conductive movable electrode which is elastically deformable in response to an input operation so as to vary the size of the gap; an input operating section engageable with a coupling portion formed to project from the elastic member; and an insulating film formed on the fixed electrode; wherein the portion of the movable electrode facing the fixed electrode is tapered such that the size of the gap progressively varies from an outer peripheral region of the fixed electrode towards the center of the fixed electrode.
This arrangement permits a large variation of the electrostatic capacitance created between the movable electrode and the fixed electrode per unit amount of movement of the input operating section. The large variation of the electrostatic capacitance can be detected without fail, thus offering a high degree of inputting precision of the input device.
Preferably, the tapered movable electrode has a portion which is held in contact with or in the close proximity of the outer peripheral region of the fixed electrode, and is configured such that the size of the gap progressively increases from the outer peripheral region towards the center of the fixed electrode. When the input operating section is manipulated by a user, the portion of the movable electrode facing the outer peripheral region of the fixed electrode which has a greater area than inner peripheral region is pressed onto the outer peripheral region of the fixed electrode across an insulating film, whereby the amount of variation of the electrostatic capacitance is further increased.
Preferably, the insulating film has a thickness not greater than 20 xcexcm. This feature provides a large electrostatic capacitance created between the movable electrode and the fixed electrode, as well as a large amount of variation of the electrostatic capacitance, thus offering a high degree of inputting precision of the input device.
The above and other objects, features and advantages of the present invention will become clear from the following description of the preferred embodiments when the same is read in conjunction with the accompanying drawings.